The proposed research has two principal objectives: (l) identification and characterization of the porcine ovarian granulosa cell (GC) FSH receptor; and (2) determination of the fate of the receptor after interaction with FSH. The project will utilize in vitro techniques to test the hypothesis that down regulation of receptor is at most a minor component of the mechanism of action of FSH in the ovary. The Principal Investigator specifically proposes to: (l) prepare purified porcine FSH: (2) iodinate pFSH to high specific activity with retention of biological activity; (3) characterize binding of FSH to intact GC, to crude and purified GC membranes and to GC receptor solubilized with non-ionic detergent; (4) determine some physicochemical properties of the GC FSH receptor by analytical gel filtration chromatography, sucrose density gradient ultracentrifugation, lectin affinity chromatography, isoelectric focusing and gel electrophoresis; (5) directly label the FSH receptor in intact GC chemically in conjunction with affinity masking/ummasking, or metabolically in culture; (6) determine the fate of the labeled receptor after exposure of GC to FSH; (7) correlate FSH receptor content with adenylate cyclase activity; and (8) compare rates of FSH receptor synthesis for small follicle and large follicle GC. The results of these investigations will permit formulation of a model of the dynamic regulation of the FSH receptor, hopefully applicable to other glycoprotein hormone membrane receptors. An understanding of FSH receptor-adenylate cyclase interactions would facilitate elucidation of the mechanism by which FSH transmits its signal to the GC and elicits cellular responses. In other words, these studies would advance the knowledge of how the pituitary gland controls follicular maturation and regulates fertility in the female.